The application is in response to RFA-CA-08-024, entitled "Measures and Determinants of Smokeless Tobacco Use, Prevention, and Cessation" (R01). This is a joint application between the University of Tennessee Health Science Center, the United States Air Force, and Mayo Clinic College of Medicine. Smokeless tobacco (ST) is tobacco consumed orally and not burned. The prevalence of ST use among Americans aged =12 years has increased significantly from 2004 to 2006 (3.0% vs. 3.3%). ST use is estimated to be the greatest exogenous source of human exposure to carcinogenic nitrosamines and has been associated with oral and extra-oral cancer as well as cardiovascular and cerebrovascular disease. Evidence exists suggesting the tobacco users who report using both ST and cigarettes (i.e., "dual users") may be at increased risk for cardiovascular events compared to those who smoke only cigarettes. Phillip Morris USA and R.J. Reynolds, two of the world's largest cigarette manufacturers, have entered the ST market. Phillip Morris USA has developed "Marlboro Snus" and R.J. Reynolds has launched "Camel Snus." Both products have been designed to appeal to smokers and potentially undermine cigarette smoking cessation attempts motivated by clean indoor air policies and increased cigarette excise taxes. At the same time, ST is also increasingly being proposed as a harm reduction strategy for cigarette smokers. As such, it is anticipated that the prevalence of ST will increase in the future. One of the highest risk groups for adoption and use of ST is the U.S. military. As indicated in the RFA, "A survey of U.S. military personnel in 1994-95 found that approximately 24% of white men on active duty used smokeless tobacco." More updated results indicate that 14.5% of all military personnel regularly use ST, 21.6% of white males aged 18-24 are users, and the Air Force is going against secular trends in the military in that ST use is on the rise. Moreover, research from our collaboration is showing that the overwhelming percentage of ST users are "dual users," regular users of ST and other tobacco products (see Previous Work). We suspect that the high prevalence of dual use is partially due to the restrictions placed on smoking at most military bases. Since dual users have a higher estimated nicotine exposure and are less likely to quit smoking relative to those who use cigarettes or ST exclusively, obtaining onset and cessation data on these individuals in the military is a very high priority. Based on this background, we propose the following Specific Aims: (1) To enroll approximately 30,000 Air Force recruits from Basic Military Training (BMT) at Lackland Air Force Base in San Antonio, TX. (2) To conduct a baseline assessment at the end of BMT, a time when all recruits have been tobacco free for eight weeks. (3) To evaluate ST and dual tobacco use (ST + cigarette smoking) initiation and cessation at a one and two-year follow-up.